Amblyopia is traditionally classified by the associated condition thought to be responsible for the amblyopic defect--strabismus, anisometropia, or deprivation. The primary objective of this project is to create a classification system for amblyopia based on functional visual loss -- a classification system based on a broad spectrum of clinical, psychophysical and oculomotor abnormalities that could supplant or supplement the traditional approach leading to better diagnosis and treatment. A pilot project on 215 subjects (including 64 amblyopes, 58 recovered amblyopes, 58 "at risk" subjects with the associated condition who have never been amblyopic, and 35 normal subjects) has demonstrated that this objective is feasible. The information derived from the 20 laboratory measurements made on each subject in the pilot sample was not simply redundant with their measured Snellen acuities and/or their clinical diagnoses. Therefore, laboratory data, in conjunction with clinical measurements, can be used to create statistically-valid classes that are significantly different from each other. In the proposed project, 500 subjects (250 amblyopic, 100 "at risk", 75 recovered, 75 normal controls) will be administered a modified set of other clinical, psychophysical and oculomotor tests used in the pilot phase. The resulting data will be analyzed: -To determine the set of visual behaviors that distinguish amblyopic eyes from normal eyes. -To determine clusters of visual behaviors that define different types of ambloyopia. -To determine the correlation between types derived from psychophysical and oculomotor measures and clinical measures collected on the same subjects. The statistical techniques of cluster analysis will be used on the measured clinical, psychophysical and oculomotor variables to create the desired classification system. The age range for the subjects will be from 8 to 40 years.